1. Field of the Invention
The present invention relates to an apparatus for intimate mixing of solids, liquids, gases, and more particularly relates to aeration associated with wastewater treatment.
2. Description of Prior Art
There are many different types of aerators used for a variety of diverse needs and processes. There are disadvantages to all of them.
Surface aerators contain motor driven propellers and are anchored in place on the surface of basins or ponds to agitate wastewater and transfer oxygen. Most surface aerators in use require 25 to 100 horsepower each and most installations have multiple units to fulfill aeration requirements. High-energy consumption makes them expensive to operate. Surface aerators also have moving components in direct contact with the water they aerate. This causes time consuming downtime and high maintenance costs. Due to their size, their weight and their placement in large bodies of water another disadvantage is in the need for crane type equipment to remove them for maintenance, repair or replacement.
Fine bubble diffusers are another type of aeration device. This type of device is placed at the bottom of basins with water depth of 4 to 5 meters (13 to 16 feet). The depth at which these units are placed requires relatively high pressures to overcome the weight of the water above them. High pressure translates into high-energy consumption, which translates into high costs.
As its name implies, the openings in these units that discharge air into water are miniscule in size. This makes them susceptible to clogging.
Another type of aeration device is the Sparging Ring. Sparging Rings are placed at the bottom of basins at depths of 4 to 5 meters (13 to 16 feet). Sparging Rings require relatively high pressure, have high-energy usage and high costs. Turbines are used with these devices to break up the size of the air bubbles and to mix the large volumes of liquid contained within the basin. Turbines are high-energy consumption devices, have moving parts in direct contact with the liquid and are high maintenance devices.
One of the newer types of aeration devices is the Aspiration Stripper. This type of device aspirates free air. Liquid to be aerated is pumped through a multitude of orifices within the unit. In order to aspirate air, liquid is pumped though these devices at pressures that may exceed 50 PSI. High pressure requires high-energy input, which translates to high costs. The small, elongated orifices in the units make them susceptible to clogging. Pre-filtering is often required. This type of aeration device is limited in the amount of aspirated air available to transfer oxygen into liquid. When a process has high oxygen demand, this type of device has to recycle liquid already processed. The susceptibility to clogging, high-energy requirement, and recycling requirement in high oxygen transfer applications are disadvantages of this type of aeration device.
In summation, all of these Prior Art aeration devices have distinct disadvantages.